Shock absorbing strut



Dec' 12, 1944 H. w. MA-rlNGLY 2,364,865

SHOCK ABSORBING STRUT Filed 061'.. 7, 1941 Sheets-Sheet 1 #lill mvENToR Z 3 166794044 8 3 52222223 1.33% 3 72 4W |f 1:02.11 1 :7W VVr rL a m.. 9m.

Dec. l2, 1944. H. w. MATTINGLY SHOCK ABSORBING s TRUT 2 sheets-sheet 2 I Filed Oct. 7. 1941l Patented Dec. 12, 1944 UNITED STATES AlfeTlN'r oFF-ICE; Si

j 2,364,865 SHOCK ABSORBING sTRU'r Harold W. Mattingly, Las Angeles, cali'r., assign- 'f or to Axelson Manufacturing Co., Los Angeles, Calif., a corporation of California Application october 7,1941, serial Na. naastl Q claims;

My invention relates broadly to improvements in shock absorbers and has particular reference to shock absorbing struts for use with the landing gear of aircraft.

Shock struts for use in connection with airplane landing gears areusually of thev combination hydraulic and pneumatic type wherein a pair of telescopically assembled cylinders are held in their extended position by means of air preslsure maintained within the cylinders and the shocks of landing the airplane are absorbed by the transfer of liquid from one ofthe cylinders yto the other through restrictedr openings or orifices. `In order to permit the relatively free contracting motion of the cylinders relative to each other but to snubor check the extending movement of the cylinders, the cylinders are so assembled relative to each other that during the contracting movement 'an auxiliary chamber is provided of 'gradually increasing Vvolume as the cylinders telescopically move toward each other while uponthe extending movement of the cylinders this chamber is gradually 'reduced in volume.-

Y Thus by permittingY a small amount of the liquid to ow from the cylinders into this chamber during the contracting' motion in a" relatively free manner, and then tov permit the return of this liquid fromthe chamber to the' cylinders by a restricted path or retarded motion, the snubbing or checking eiectis accomplished.

It` is an objectof my invention to improve upon the construction of shock absorbers ofthe character just described by providingv a Irelatively inexpensive'mechanism by which the rate of flow from the cylinders to the auxiliary chain'-` ber may be'controlled and whereby the return flow from the chamber'to the cylinders may be readily restricted to provide anydesired or predetermined rate of motion of the Vcylinders dur'- ing the expanding stroke.'Y

Another object 'of lmy invention is t' pro# vide a positive and accurate meansfor adjusting the rate of now of the liquid between the chamber and the cylinders which may be accomplished at any time during the life of the shock. struts.

Another object of myiinvention is tol-Provide an improved and simpliedconstruction of a metering orifice plate which may be 'employed to meter the passage -of Viluid between the two cylinders. 1'

Other objects and .advantages of my invention will be apparent from the study of the following specications, read in connection withthe accompanying drawings, wherein i(o1.A 267-64) Fig. 1 is-a vertical elevational view of afshock vstrut constructed in accordance withv my invention with portions -of the mechanism broken away `and shown in section, the strut being shown i'A5 in fa substantially completely contracted position;

Fig. 2 is `an enlargedl fragmentary vertical sectional view illustrating the metering ports and valve structure employed to control the transfer E1-0 of uid between the cylinders and the auxiliary chamber with theparts in the positions they will assume during the contracting lstroke o'f"the strut;

Fig. 3 is a vertical sectional view similarv to Fig. 2l and illustrating the positions ofthe parts during the expanding stroke of the strut;

Fig. 4 is vafdeveloped vview of a portion of'the inner cylinder, illustrating the location ofthe voriiices and Valve ports; and f f Fig. 5 is a detail'fragmentary vertical sectional `view of aA portion of: vthe strut illustrating the construction and` location .of I the" metering .orice plate and `the-guiding and packing `structure employed between the-'two cylinders.'y

Referring to the drawings, I have/illustrated iin Fig; v1 a shock strutfof a type adapted foruse on aircraft. landing gearwhich comprises an i outier cylinder member I, to the upper end of which is iixed asuitable bracket 2. by whichtheupper endl of thev strutimay besecured to the Wings or-'frame of the aircraft. Telescopically assem;

` bledwithinrthe outerV cylinder'l is `an inner cyl# -inder 3,.the lower-end voflwhich isformed with .or has secured thereona bracket 4 bywhich the yinner cylinder-may be coupled to the; landing gear of `the aircraft. r l f The inner cylinder 3 isl provided adjacent its lower` end `with a partitionr orclosure ,5 consti'- tuting a complete closure 'or cylinder head for Y40 the lower end of 'the inner cylinder 3. VA piston 6 is disposed within the inner cylinder 3 v'and is adapted to be rigidly disposed relative to the outer cylinder I rand `movable 'therewith aspby mounting the piston `6 upon thelower end of a pistonsupporting tube Twhich-is' in turn-rigidly secured lto 'the bracket 2 as indicatedv atil.-

The lower end ofithebracket 2 is preferably formed as acylindrical member which may be inserted into' the upper end oi'y the outer cylin- A5,0 der-I and'there constitute a closure or cylinder head for the outer cylindervl. f i Thus by partially iilling'the assembled cylinders withoil or somenon-compressible liquid and supplying'airor other compressible gas to lthe interior-off the structure to build up a preadapted to be secured in the'piston'.

determined pressure therein, the air acts as a vspring to urge the cylinders toward their fully vtherethrough intercommumcating the lower portion II of the cylinder 3 with the Vupper -por` l tion II)l of this cylinder, the xed sized opening being preferably formed in an* orice :plate 9 As is inustrated paruemarly in Fig. 5,the piston 6 is constructed as a ring-like memberpthe interior of which is threaded as indicated at I2 I while at the extreme lower end of the ring-likeA piston Ii there is provided anfinwardly :extending :flange I3. The vorifice plate A9 is formed as asubstantially disc-like member, the outer edge `of which is threaded Lto .be received yin the threaded boresIZ -of the piston `I andthe lower surface of the plate 9 is preferably under-cut `to forma shoulder member I4-adapted to rest -uponl 'the' upper surface of .the flange `I3 of the :piston l `Ii 'when the orifice :plate Ais assembledwithin the piston 6. While' I have illustrated y .the Vorifice plate v9 as having itsouter edge threaded, by which it mayy be screwed into the threaded bore I2 with ,fthe

use .of any suitable Spanner;v wrench or pinA Awrench engaging wrench fbores 15, .it will be;

apparent that the orifice plate 9 may be merely dropped into-thepiston 6, and be clamped in place Vtherein* `by vmeans of a vsuitable-lock wash er or nut I6 threadedintothe bore I2 -byla-smif.

larspanner or pin type of wrench.

The-upper .endof the threaded `bore I2 fof the' piston '6 may :be utilized -as the .means .for coupling the ipist'onto the piston supporting tube l as by threadingzthe lower end=of the tube l'I intdthe piston 61 and rlocking thelsameiniplace by-means offsutable locking'screws I'I :projected radially" through -,the.fpiston 6 and into and through suitable clock bores or'holes I8 formed` in the lower fend 'ofrthe .pistonjtube 7.

By utilizing the Yconstruction just-:described and then ythe assembled :structure may '.be :se-

curedwtoxthe piston support tube 11 :as :a second :orv subsequent operation by' 'which any virregularities or imperfections in the "length ofV the support tube lI may be compensated for by yreguylating the extent to 'whichfthefpiston support `.e"1.1rther,by`

tube is projectedrinto the 4piston =6. employing theA threaded connection `between the orifice plate' and the piston Gand the vlock washhave illustrated a metering pin 20 mounted upon and rigid with the partition or end closure 5 for the cylinder 3 and projecting upwardly therefrom-to enter and restrict the orifice I9 when vthe cylinders I and 3 are moved toward their telescoped or contracted positions, the metering pin 20 beingy provided either with `an external shape varying its effective diameter at different `portions of its 'length or-jitmay be provided with one or more 'grooves 2I ofvariable depth at different portions along the length of thev pin 20 to achieve the same result of variably restricting .thepassage of uid through the orice I9 during different portions of the stroke.

` By employing a tubular member as the support for lthe piston 6, it is necessary to provide kforfree 'passage of fluid between the interior andvexterior of this tube and for this purpose a plurality of holes 22 may be provided through thewalls of the tube I so that as the fluid is transferred lfrom .the lower portion of the cylinder 3"through: the metering `orifice I9;y it may have free access tothe interior `ofthe cylinder.

f yis vprovided between theinner cylinder V3 and the it'wi'll be apparent .that `,the piston and iits ori-` flce plate may. beassembled ;as Aone operation a metering-,pinby so selecting `the.diameter of the central.v boreor orifice I9. vthrough the plate as to.permitgthe'desiredtransfer of fluid from` .the -lowerlziortioniS- of the cyl-inder- 3 toy theV upper portionof this cylinder .under theloadsrfor which regulatedwand varied duringdifferent ,portions of the strokeof the strut. For this purpose I l'7o the strut is designed, orthe'orifice plate imay` outer cylinder I as by forming the.inner.cylinder l `3 kwith a diameter somewhat smaller-than-.the

internal -diameterfof 4the cylinder I land provid- .ing spacers or `bearings-betweenthe,cylinders I and 2l `to vcloseboth ends-ofthe f chamber 23.-

As illustrated. ,the ^lower l end of the kouter cylinder I yis fprovided'withv an enlarged diameter portion `Zit-forminxgfat its junction iwith'the smaller diameterof .thecylinder -I an internal shoulder 25 against which Ymay .be rscrewed a packing support washer 26vconstitutingV abearing member againstwhich apacking :ring assembly, may bear, the,packingeringgassembly ypreferably being-zconstructed as -fannular chevron packing V2l disposed between supportingr metal packing rings l28and29. v A

To holdthev packingv vassembly in place and to provide forthe necessary adjustment of the pressure. exerted Aon the packing;v a bearing -sleeve 30 maybe inserted into the. lower Aendfof` the cylinder'l to' ill lthe space between .the enlarged vportion 24-2and the rvTadjacent external -surface ofthe cylinder thelength of the bearingmmber 30 being such that its lower 'edge will project slight# ly beyond therlowerfend of .the cylinder Iwheref by ya .cap or nut l3-I vthreaded -onto the-:end of the cylinder-I maybe tightenedorloosened 4to press the bearing sleeve 30 againstapacking assembly with any desired forcethe,nut 3| vbeing preferably locked .in .its position by means, of 1a set screw-32. y `j lThe .upper end; of the s chamber :23 is iclosed '01T by means of.v a. bearing sleeve J33y threaded or otherwise 1- adjustably `mounted upon and moving with the `,upper end ,of'theinner cylinder 3 and extending across -.the annular space .between the .ed particularly in Figs.` 2 and 3. The size of each of the ports and the number of them is preferably -selected that their combined areas'will provide fo'r a relatively free and unrestricted transfer of fluid to and from the chamber 23. Thus on the contracting stroke of the strut the chamber 23 l"will gradually enlarge its volume and the fluid `will readily pass from the interior .of the cylinders to the chamber 23.

On the expanding stroke ofthe-strut the rate of movement of the cylinders relative to each other may be restricted in any desired amount by providing avalve structure which will partially close each of the .passages or ports 34. One such valve structure is illustrated herein as comprising a sleeve member 35 freely slidably mounted upon the exterior of the inner cylinder 3 and having a wall thickness somewhat less than the distance across the annular space between the inner and outer cylinders. Thus when the cylinders are moving during their contracting stroke, the ow of fluid through the ports 34 and downwardly past the valve sleeve 35 will,force the valve sleeve 35 downwardly to its lowermost position in abutment with a shoulder 36 formed on the cylinder 3 and with the upper edge of the valve sleeve 35 entirely free of the openings or ports 34, permitting the full area of each of the ports to be effective during that stroke.

During the expanding stroke, as illustrated in Fig. 3, the flow of uid from the chamber 23 back through the orices or ports 34 and upwardly past the valve sleeve 35 will cause this sleeve to be moved upwardly and across the ports or orifices 34, closing off these ports. In this position of the valve sleeve 35, its upper edge is in abutment with the lower edge of the guide bearing 33 and I utilize this abutment to regulate or control the extent to which the valve will close off each of the ports 34 by forming the lower edge of the bearing sleeve 33 with arcuate not'ch recesses 3l so disposed as to be alignable with the orices 34 and permit free passage of iluid through the orices while a portionof the material of the guide bearing 33 projects downwardly between each pair of adjacent ports. Thus when the valve sleeve 35 has but partially covered the ports 34, it will be brought to a stop and the ef,- fective area of the ports for the vreturn of the fluid is restricted to any predetermined amount.

By employing the valve and bearing structure just described, but a single set of transfer orifices 34 is required and by forming the recesses 3l of slightly larger radius than the radius of the orifices 34, a ready adjustment of the rate of return iiow from the chamber 23 may be provided merely by screwing the bearing member 33 down or up relative to the cylinder 3 so as to dispose the lower edge of the bearing 33 as a limit stop for the valve sleeve 35 at different positions in its upward movement from a maximum opening to substantially fully closed.

Also the effective area of the transfer ports 34 during the expanding stroke may be adjusted by rotating the bearing member 33 relative to the ports 34 until they close oif or obscure portions of the ports. The bearing member 33 may'then be locked in any adjusted position by means of suitable set screws 38.

By referring to Fig- 1 it will be observed that at the fully extended positions of the cylinders I and yIl the packing supportwasherv 26 Will 'engage the` valve sleeve 35 and will act to positively move this valve to its orifice obscuring position, 'thevwasher 26 being' counter-bored, as indicated at 39, to provide a shoulder 40 adapted to engage the lower edge of the valve sleeve 35.

It willbe observed therefore that I have provided a shock strut construction wherein the manufacture of the strut is considerably facilitated by permitting the pre-assembly of parts at one stage of the manufacturing operations prior to the completed nal assembly and wherein a' ymaximum of adjustment may be made either during assembly or in the field for the regulation of the rates of either the expansion stroke or the contracting stroke of the strut. v v I While I have shown anddescribed the preferred embodimentV of my invention, I do not Vdesire to be limited to any ofthe details shown or described therein, except as dened in the appended claims.

I claim:

l. In a shock strut, a pair of telescoping cylinders annularly spaced from each other .to dene a chamber therebetween, a port extending through one of said cylinders and communicating with said chamber, a valve sleeve slidably mounted on said one cylinder for sliding movement between one position free of said port and lanother position covering said port, a fixed sleeve limit the extent of the partial closingoff of said port by said valve sleeve.

2. In a shock strut, a pair of telescoping cylinders annularly spaced from each other to dene a chamber therebetween, a port extendingr through one of said cylinders and communicating with said chamber, a sleeve fixed on said cylinder and having a recess in one edge thereof disposed aboutsaid port, a valve sleeve slidably mounted on said cylinder between one position free of said port and another position closing off said port and engageable with the edge of said .first sleeve when said port is but partially closed to limit the extent of closing off of said port,

and means adjustably mounting said first sleeve on said cylinder for movement to positions obscuring said port to adjustably vary the effective area of said port.

3. In a shock strut, a pair of telescoping'cylinders annularly spaced from each other to define a chamber therebetween, a plurality of ports extending through one of said cylinders and communicating with said chamber, all of said ports being disposed in a single plane transverse to the axis of said cylinder, a sleeve valve slidably mounted upon said cylinder for movement across said ports, stop means associated with said cylinder to engage said sleeve valve and limit its movement across said ports when each of said ports has beenv but partially closed 01T, andv means mounting said stop means on said cylinder for adjustable movement therealong relative to said ports for varying the limit to which said ports will be partially closed by said sleeve valve.

4. In a shock strut, a pair of telescoping cyl- `inders .annularly :spaced from each fother Yto 'dexnefa chamber therebetween, a pluralityrof ports extendin'g'through one of said cylinders and communicating With said chamber, the centers of all oflrsaid ,ports'being -disposed in a :single plane transverse to vthe, axis of `said cylinder, 1a Lsleeve valve slidably mounted upon said cylinder for movement across -said ports, :and a sleeve 'surrounding said cylinder and .fixed thereto and having applurality of recesses formed in that end vfof .the 'sleeve 4disposed adjacent said ports to provide la plurality of feetr disposed between adjacent ports and extending in the direction of the sleeve valve to a :position beyond the plane of said ports lto engage and limit the movement of the sleeve valve across said ports lWhenveach of said ports has been butvpartiallyclosed off.

-5. In combination with va shock strut including "a pair vof cylinders telescopically `assembled one IUi ra'sases withinthe other, .apiston supported :intnxed .relation to vsaid outercylinderbymeans of a piston tube vextending Withinnsaid inner cylinder and Ydisposing ysai-d pistonwithin said .inner cylinder,

and a metering orice-platecassociated'with'said piston :for controlling l-the'ratef' of transfer "of liquidbetween said-cylinders; of a threadedcounrter--loore extending longitudinally .of :said piston4 and Vterminating 'in la plate supporting kiiange at "theend of said Vpiston furthermost from the point -at different :distances ifromxithe :point of :connection of said piston to said outerxcylinder.

:HAROLD v MATTINGLY. 

